Cytogenetic Analysis of Two Species of Brachyhypopomus (Hypopomidae): New Inferences about Karyotypic Diversification of Grass Knifefish

Mapping of Repetitive Sequences in Brachyhypopomus brevirostris (Hypopomidae, Gymnotiformes) from the Brazilian Amazon

“…draco [ 18 ], to 50 for Hypopygus lepturus [ 13 ], Steatogenys duidae , and Steatogenys elegans [ 41 ]. Using ChromEvol, (version 2.0), a software package that implements a series of likelihood models regarding the pathways by which the evolution of chromosome number proceeds, Takagui et al [ 18 ] estimated that 2n = 34 is the ancestral condition for this clade, just as in B. beebei and B. hamiltoni , which have 40 and 36 chromosomes, respectively. B. brevirostris also had its karyotype originated by centromeric fissions.…”

“…Previous studies on the location of the Nucleolus Organizer Region (NOR) in Hypopomidae are only available for two genera. NOR presents a multiple system in Brachyhypopomus gauderio [ 17 , 18 ] and in Microsternarchus bilineatus from Rio Negro—AM [ 46 ], and a simple system in Brachyhypopomus cf. draco [ 18 ] and Microsternarchus aff.…”

“…Karyotypic data were described for 12 of the 28 species [ 13 , 14 , 15 , 16 , 17 , 18 ] ( Table 1 ). Different species of Brachyhypopomus differ in 2n (26 to 44), KF, and the number of chromosomes carrying NOR, and may be simple or multiple ( Table 1 ).…”

“…Different species of Brachyhypopomus differ in 2n (26 to 44), KF, and the number of chromosomes carrying NOR, and may be simple or multiple ( Table 1 ). There are also karyotypes with the multiple sex system X 1 X 1 X 2 X 2 /X 1 X 2 Y found in three species: B. pinnicaudatus (2n = 41/42) and B. flavipomus (2n = 43/44), both from Mamirauá—AM [ 15 ], and B. gauderio (2n = 41/42) from the Tietê River—SP [ 16 ], from Porto Rico—PR [ 17 ], and the Paranapanema River—PR [ 18 ], all from the Upper Paraná River. Brachyhypopomus brevirostris , from the Madeira River in Humaitá—AM, was the first species of the genus to have its karyotype studied, showing a diploid number (2n) of 36 chromosomes and a karyotypic formula (FC) of 6m/sm + 30st/a [ 13 ].…”

Doubling down on polyploidy

“…Schneider et al ., 2017; Stull et al ., 2021; Ibiapino et al ., 2022), and also for animals and fungi using chromosome count sources specific to those groups (e.g. Campbell et al ., 2016; Takagui et al ., 2022). The development of large, synthetic phylogenies, such as the spermatophyte phylogenies of Smith & Brown (2018), has also facilitated the application of these tools across vast phylogenetic scales (e.g.…”